Speakers having a curved diaphragm, such as Ryffel-type speakers, are known as a type of various speakers for reproducing sound. For example, Patent Document 1 (Japanese Utility Model Patent No. B6336889) discloses an illumination apparatus with a speaker where a diaphragm (speaker diaphragm) is made of a light-transmittable material and used as a protection cover of a lighting lamp. In this illumination apparatus with the speaker, the diaphragm is installed on a box-shaped frame.
Furthermore, Patent Document 2 (Japanese Patent No. 3521319) discloses a speaker where two vertically split cylindrical diaphragms, namely having longitudinally divided cylindrical surfaces, are integrally disposed in parallel in the same direction and the edges of the diaphragms are fixed to a frame. In addition to the above-mentioned speaker, Patent Document 2 also discloses a speaker where two sets of vertically split cylindrical diaphragms, closed from each other, are disposed integrally in parallel in a circumferential direction and a speaker where four vertically split cylindrical diaphragms are disposed back to back in parallel. These four diaphragms are configured so that the joining sections of the respective diaphragms are supported by the magnetic circuits or the voice coil bobbins disposed inside, and all the diaphragms are disposed so that the curved faces thereof are directed outward.
Moreover, Patent Document 3 (Japanese Patent No. 5191796) discloses a speaker where two diaphragms are provided in parallel and both the end sections of the diaphragm are elastically supported by a frame so that the central section of the diaphragm is curved. The frame of this speaker has an almost line-symmetric shape where a pair of flat plate sections is connected to each other with a central connection section.
The structures of the speakers disclosed in Patent Documents 1 to 3 described above can be applied to microphones having an operation principle opposite to that of speakers. As disclosed in Patent Documents 1 to 3 described above, speakers having a curved diaphragm are configured so that the end sections of the diaphragm are fixed to a rectangular frame, and the diaphragm and the housing of each speaker are separated in the external appearance of the speaker, so that the speakers have similar external appearances. But since the tastes of consumers have diversified, it is desirable to further improve the design property of this kind of electroacoustic transducer.
In addition, in these speakers disclosed in Patent Documents 1 to 3, design and acoustic characteristics utilizing the shapes of the curved diaphragms have not yet been achieved.
There remains a need for an electroacoustic transducer having a curved vibration face and being excellent in acoustic characteristics and excellent in design property. The present invention addresses this need.